| Five experiments for this thesis were conducted to characterize organic Mn sources chemically, and investigate the effects of either dietary Mn source and level or intravenously injected Mn source on growth performance, incidence of leg abnormality, tissue Mn content, MnSOD activity in heart mitochondria, and its gene expression, so as to evaluate their relative bioavailabilities for broilers.Experiment 1. Studies of chemical characteristics for organic manganese sourcesTwelve organic Mn sources were collected from China and abroad, and characterized together with reagent grade MnSO4 ?H2O. The organic Mn sources were five Mn-methionine products (Mn-Met A~E), two Mn-proteinate products (Mn-Pro A~B), and five Mn-amino acid products (Mn-AA A~E), respectively. Mineral concentrations and amino acid contents in Mn sources were determined by ICAP-9000 emission spectrophotometry and HPLC. Structural characteristics were determined by infrared spectroscopy. Solubilities of Mn sources were measured in 0.4%HC1, 2% citric acid, neutral ammonium citrate, water, 0.2M HC1-KC1 buffer (pH2), and 0.1M KH2P04- K2HP04 buffer (pH5). Complexed Mn percentages in soluble fractions of Mn sources were measured in 0.2M HC1-KC1 buffer (pH2) and 0.1M KH2P04- K2HPO4 buffer (pH5) by gel filtration chromatography. A polarography experiment was carried out with a hanging mercury drop electrode to determine complex quotients (Qf) of Mn sources. The results showed that: 1) Mn concentrations ranged from 6.18 to 17.44% in organic Mn sources, however, some sources also contained some macro- or micro-elements, such as Mn-AA D containing 13.14% Ca and 3.36% Mg, Mn-Met A and D containing 1.46% or 2.47% Fe, respectively, Mn-AA A containing 1.14% Cu, and Mn-AAB containing 5.32% Zn; 2) Molar ratios of total amino acid content to Mn in 10 organic Mn sources tested changed from 0.04:1 to 1.83:1, in which molar ratios in Mn-Met B and C, and Mn-AA A.^ B and C were over 1:1, and molar ratios in Mn-Met D and E, Mn-AA D, and Mn-Pro A and B were below 1:1; 3) Organic Mn sources had characteristic peaks of complexed Mn; 4) Except that the solubility of Mn-AA D in 0.4%HC1 was 90.3%, and Mn-Pro B and Mn-AA D in pH2, 0.2M HC1-KC1 buffer was 74.1% and 85.3%, respectively, other organic Mn sources were highly soluble in 0.4%HC1, 2% citric acid, neutral ammonium citrate, and pH2. 0.2M HC1-KC1 buffer with more than 95% solubility. Solubility of Mn sources varied from 5.8% to 99.8% in water and pH5, 0.1M KH2P04- K2HPO4 buffer; 5) Under this experimental condition, no complexed Mn was found for these organic Mn sources filtrates from pH2, 0.2M HC1-KC1 and pH5. 0.1M KH2P04- K2HP04 buffer; 6) Organic Mn sources had different complex strengths. Mn-Met A~E. Mn-AA D and E had Qf values below 10, showing a weak complex strength, and Mn-Pro A and B. andMn-AA A and B had Qf values between 10 and 100, indicating a moderate complex strength, while Mn-AA C had a Qf value (115.4) more than 100, showing a strong complex strength. The results indicate that these organic Mn sources varied considerably in chemical characteristics, and this study has set up a foundation for further investigations of the correlativity between complex strengths of organic Mn sources and their relative bioavailabilities for broilers in following experiments..Experiment 2. Relative bioavailabilities of organic Mn sources with different complex strengths for broilers fed diets containing a normal level of calciumAs the complex strength of organic Mn sources is the most important of all chemical characteristics mentioned above, which might be related to their Mn utilization in the body, three organic Mn sources with different complex strengths were chosen for this study from 12 organic Mn sources tested above. They were Mn-Met E with the weak complex strength (Qf 3.2, 8.27% Mn), Mn-AA B with the moderate complex strength (Qf 45.3, 6.48% Mn), and Mn-AA C with the strong complex strength (Oj 115.4, 7.86% Mn), respectively. Therefore, experiment 2 was conducted using a total of 624 day-old...
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